4 Marine Heatwaves 2024

Code

import sys

sys.path.append('../../')
from script_IDS import fun_script_IDS

import pandas as pd

cciea_yr = 2024


fn_meta = './metadata.csv'
df1 = pd.read_csv(fn_meta)
cell2_wnt = ['Component_Section', 'Subcomponent', 'ERDDAP_Dataset_ID', 'PI', 'Contact']

ds_id_hc = 'cciea_OC_MHW'
ts_id_list = ['cciea_OC_MHW_HC']
vec2_hc, ds_id_lbl_hc, rgn_lbl_hc = fun_script_IDS(df1, cell2_wnt, ds_id_hc, ts_id_list)

ds_id_ma = 'cciea_OC_MHW'
ts_id_list = ['cciea_OC_MHW_MA']
vec2_ma, ds_id_lbl_ma, rgn_lbl_ma = fun_script_IDS(df1, cell2_wnt, ds_id_ma, ts_id_list)

ds_id_mi = 'cciea_OC_MHW'
ts_id_list = ['cciea_OC_MHW_MI']
vec2_mi, ds_id_lbl_mi, rgn_lbl_mi = fun_script_IDS(df1, cell2_wnt, ds_id_mi, ts_id_list)

Description Marine heatwaves (MHW) occur when ocean temperatures are much warmer than usual for an extended period of time; they are specifically defined by the difference between the current temperature and the expected temperature for a specific location and time of year [1]. MHWs are a growing field of study worldwide because of their effects on ecosystem structure, biodiversity, and regional economies.

Indicator Category Climate and Ocean Drivers

Data Steward Schroeder

Erddap Dataset ID cciea_OC_MHW, cciea_OC_MHW, cciea_OC_MHW

CCIEA timeseries ID cciea_OC_MHW_HC, cciea_OC_MHW_MA, cciea_OC_MHW_MI

Region NA, NA, NA

Public availability statement Source data are publicly available.

Additional Information There is growing recognition that marine heatwaves can have strongly disruptive impacts on the CCE (Morgan et al. 2019). Based on an analysis of sea surface temperature anomalies (SSTa) obtained from satellite measurements (OISST); we define marine heatwaves as 1.0 times when normalized SSTa >1.29 s.d. (90th percentile) of the long-term SSTa time series at a location, and lasts for >5 days; which are analogous to the thresholds suggested in Hobday et al. (2016). Here, we further report on statistics concerning large heatwaves (LHW) which were tracked through space and time, with LHW defined as those heatwaves with an area > 400,000 km2 (these denote the top 20% of all heatwaves by area as measured since 1982 when satellite data became available for tracking. For more information on MHW see https://www.integratedecosystemassessment.noaa.gov/regions/california-current/california-current-marine-heatwave-tracker-blobtracker.

Figures

Figure 4.1: Monthly average of MHW time series.

2024 Conditions

Monthly MHW sum area Figure 9.1 was above the long-term mean during summer and fall 2024.
Winter, Spring and Summer MHW sum area Figure 9.2 (b) had 2024 values lower than 2023.
Heat wave cover during the winter 2024 Figure 9.2 (a) was above 1 sd, this probably can be attributed to El Niño elevating coastal temperatures Figure 8.2 (a).
Heat wave cover during winter and spring 2025 was low and above 1 sd during summer and fall (Figure 9.2 (a)).
Monthly MHW sum area Figure 9.1 was above the long-term mean during summer and fall 2025 – the summer area was one of the largest for the record (Figure 9.2 (b)).
The intensity of MHW has been the most consistent during the summer, where the 5-year mean has been over 1 sd (Figure 9.2 (c)).

References

Hobday, Alistair J, Lisa V Alexander, Sarah E Perkins, Dan A Smale, Sandra C Straub, Eric CJ Oliver, Jessica A Benthuysen, et al. 2016. “A Hierarchical Approach to Defining Marine Heatwaves.” Progress in Oceanography 141: 227–38.

Morgan, Cheryl A, Brian R Beckman, Laurie A Weitkamp, and Kurt L Fresh. 2019. “Recent Ecosystem Disturbance in the Northern California Current.” Fisheries 44 (10): 465–74.